1. Field of the Invention
This invention relates to detergents, lubricating oil additives and compositions, and methods of preparing detergents, lubricating oil additives and compositions. More specifically, this invention relates to novel phenolic dimers.
2. Background Art
Lubricating oil compositions, as used in the internal combustion engines and transmissions of automobiles or trucks, are subjected to a demanding environment. This environment results in the lubricating oil composition suffering oxidation that is catalyzed by the presence of impurities in the lubricating oil composition, such as iron compounds. Additionally, oxidation of the lubricating oil composition is promoted by the elevated temperatures of the lubricating oil composition during use.
The oxidation of the lubricating oil composition during use is usually controlled to some extent by the use of additives, such as antioxidants or acid neutralizers, which may extend the useful life of the lubricating oil composition, particularly by reducing or preventing unacceptable viscosity increases.
One class of antioxidants and acid neutralizers generally employed in lubricating oils are metal alkyl phenates. The metal of the metal alkyl phenates is generally an alkaline earth metal such as calcium, magnesium, or barium.
Examples of metal alkyl phenates are found in U.S. Pat. Nos. 5,330,665 and 5,162,085. The metal alkyl phenates disclosed in these patents are overbased, monomeric, alkyl phenols.
In recent years, phosphorus compounds and sulfur (from sulfonates, sulfur-containing phenates, and metal-containing dithiophosphates) derived from engine lubricants have been shown to contribute in part to particulate emissions. Also, sulfur and phosphorus tend to poison the catalysts used in catalytic converters, resulting in a reduction in performance of the catalysts.
U.S. Pat. No. 6,310,009 B1 and U.S. Publication No. 2004/0102335 A1 describe the use of an overbased saligenin derivative additive in lubricating oil compositions to reduce engine wear and corrosion that is capable of decreasing sulfur and phosphorus containing emissions.
A need exists in the art for improved additives that act to control viscosity, neutralize acid, and/or reduce oxidation. The novel phenolic dimer and the overbased phenolic dimer detergent of the present invention provide anti-wear benefit to lubricating oil compositions with a low phosphorus content and a low sulfur content.